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Monday, September 28, 2009

Heat Distribution For Solar Heating Systems

I added a section on methods of heat distribution for solar heating systems. The new section provides links to a number of ways to distribute heat to a house for a solar heating system with an emphasis on DIY approaches.

Distribution of heat for solar heating systems is complicated by the fact that solar heating systems are more efficient when producing water that is not hot by boiler standards -- that is, boilers can easily produce 160F (or more) water, while solar heating systems are going to be more efficient when producing 120F (or less) water. This makes the heat distribution more challenging, and makes some of the conventional systems difficult to use because of their reliance on high temperature water.

10 comments:

I like the idea, but unless you had that pipe and the fittings sitting around, or could get them used... It would cost more than getting an old cast iron radiator. I priced the majority of the parts at Home Depot.... Just shy of $600. That didn't include the stands..... That was for 1" pipe.....

Hi Doug,Yes -- agree that unless you have the materials on hand, or can find them as scrap it makes a pretty expensive radiator -- I just thought if was a pretty neat solution for them to work out up there. The folks at Zomeworks made some similar "radiators" from PVC pipe that would be more reasonable -- I think that these were intended for cooling, but should work for warm water heating as well (I think).This whole issue of figuring out a good and cost effective way of distributing the heat you collect from a solar system into the house is a difficult one. I hear from some people who are fine with the work involved in building collectors and tanks, but don't want to tear up their house to put a radiant floor in.What we need is some nice simple ways to distribute heat to the house. Any ideas?Thinking about this a bit more, it seems like one of the PEX/aluminum absorber sheets would work well (without the glazing). Or, maybe one of the plastic collectors normally used for pool heating, or maybe one of the Coroplast collectors (a current topic on the Yahoo Solar Heat group). It might be difficult to work these in aesthetically, but they would do a good job of radiating heat into a room at a low cost.Gary

I often times thought it would be nice to find an old car radiator that could be boxed up on the intake side of a forced air heat system, and distribute the heat that way. It would not be hot air coming out, but warm, similar to a heat pump operating.Could remove the top layer of insulation on the storage tank. It would not lose the heat fast, but faster than being insulated.I have seen the internals of baseboard heaters removed so that the fins/pipe are exposed, and put under the floor to warm an area.Best idea though, is still what you did with your floor. Not tough, but time consuming. There has to be a way to just put it under a floor...... I think you can the same way, but you would have more obstacles.

Hi Doug,Why the intake side? My thinking would be the output side to allow passive distribution of heat without the furnace blower on all the time.What about runs of PEX attached to the distribution plenum, with fins, and then insulated?

Would you cycle the blower on and off or on constantly? If constantly, I wonder if those motors can handle that and how much juice will it require.... almost .12/KWH here in Nova Scotia.But I agree, radiant floor is the better idea.

If you got a double radiator, like the big trucks have, you could likely let it run similar time frames as it would normally. The double radiators are built to dissipate a lot of heat quickly. So, when the furnace blower kicks on, you circulate the water through the radiator.Far from ideal, but it was a thought I had in trying to use some of my solar heated water, without having to retro-fit the house with radiant heat, or lots of smaller baseboard heaters.Doug

I installed an old (reconditioned) car radiator across the inlet for fresh air in my workshop. Although I installed the system for ventilation while doing composite work on my airplane, it works great when doing painting of my solar collectors as well. I ran a loop with ball valves from my wood hot water system and get pretty decent heat out of it when the water temp is at 140 degrees of better. The system is heating outside air too. A hot water heat exchanger is installed off my hot water system at my dealership for my office complex with a hydrostat that's set at 140 degrees, and it puts out great heat from the "stand alone" A/C system (actually just using the fan/blower outlet and return system). My point, heat exchangers with fans will work great with water temps in the ranges we see with solar hot water.Tom